meta Low Heritability – High Importance :: The Bullvine - The Dairy Information You Want To Know When You Need It

Low Heritability – High Importance

The Bullvine is often asked, by our readers, why we place so much, or any emphasis at all, on Health & Fertility traits in our sire recommendations ((Read more: Bullvine Performance Index and Mating Recommendations). We have decided to share with our readers some of our thoughts on breeding for traits that have low heritabilities which includes many traits in Health and Fertility.

Which Traits?

On an individual traits basis we are talking about traits like heel depth (heritability 8%), daughter fertility/daughter pregnancy rate (7%) and calving ability / calving ease (6%). On a composite trait basis this includes Feet & Legs (15%) and Herd Life / Productive Life (10%).

Heritability Hidden

Experienced breeders know that there are difference between cow families in how they transmit for these traits.  To date we have not been able to analyse the data and produce accurate genetic evaluations for these traits. It is all about how we collect the data or analyse it.  For instance when a classifier looks at heel depth he/she is to score it compared to the ideal. Yet we all know the significant effects that hoof trimming (or the lack thereof), bedding keepers and cows walking in slurry all the time can have on the scoring of heel depth by the classifier. Likewise effectiveness of routines, management, environment, nutrition and season have a significant influence pregnancy. The same can be said for calving ease. Many non-genetic factors interfere with identifying the true genetic differences between animals. Little wonder that with using our traditional data capture and genetic evaluation systems we ended up with low heritabilities.

Ignoring Was the Solution

In short the inaccuracy and lack of adjustment possible for the data we have used to evaluate these traits has meant that we have not accurately identified the best or the worst on a genetic basis. As a result the majority of breeders have ignored the genetic indexes for low heritability traits and have relied on managing around any problems their animals have had or their sire selections choices created.

So Much in Composites

With composite traits there are many individual traits combined into one overall number for FLC / Feet & Legs and PL / HL. The end result can be a high or low score for the overall but, unless we dig deeper and find out the ratings for the individual traits, we do not know the actual areas of genetic superiority or inferiority of animals. Classifiers combine many descriptive traits for feet and legs to come up with the overall score for Feet & Legs. Of course, for genetic evaluations for longevity we can not wait for a cow to complete her time in the herd. We therefore predict PL / HL by a calculation that is a combination of SCS, DPR/DF, Udder Depth and Milking Speed. These are all significant factors in how long a cow stays in a herd, but still are an estimate at best.

Genetic Evaluations

The data we have had available has not been complete enough, with enough related details, to calculate accurate genetic evaluations for these traits.  We therefore have called them low heritability traits. In fact it could well be that the extent of the data captured is not complete enough to produce accurate results.

Until about 1950 breeders used raw, unadjusted data to base their cow and bull selections on. Virtually zero progress was made in advancing the genetic merit of dairy cattle. Any advancement made was usually made at the herd level by owners that were more fortunate in the animals they owned. Evaluation techniques following that time have included dam-daughter comparisons, contemporary comparisons, BLUP (sire model) and then BLUP (animal model). These were each improvements on their predecessor yet even with the latter the accuracy of predicting a young bull or heifer’s true genetic merit for low heritability traits was only about 25-30% Reliable. The end result was that breeders paid little attention to the genetic indexes for these traits. They hoped that by breeding for the traits of high heritability, they would more often than not be lucky and make some improvement in traits like heel depth, fertility and calving ease. Over time A.I. organizations addressed the low accuracies for these traits by having at least one hundred daughters in sire type proofs and more than three hundred observations in conception, fertility and calving traits.

Progress Made

Over the past six decades, the genetic progress has gone from zero for all traits to rapid advancement for the most heritable traits (i.e. milk, fat & protein yields, stature, udder depth, teat placement, rump width, ..etc.). Over the past two decades calving ease has been a concern for breeders. With the move to hundreds of observation recorded and analysed some genetic progress appears to have been made. But not so with longevity, feet and female fertility.

Important traits

Breeders know and often state that they see these traits as being very important, in the future, to their herd’s profitability.  Labor and input expenses to treat problem animals, loss of production and animals too long in the dry pens can be robbing farms of ten to twenty-five percent of their profits. Yes, important but the means to improve genetically has not been available.

Along Comes Genomics

As our readers already know, The Bullvine strongly recommends the use of genomic indexes in making breeding decisions.  The primary reason for that is that the accuracies of the index predictions are almost double for all traits what they were with Parent Averages. For female fertility reliabilities have gone from 30% to 55% when genomic results were added in. That is huge.  It means that breeders no longer need to ignore or hope for the best with low heritability traits like they did in the past.

All A.I. sires are now genomically tested and therefore have 55 to 65% reliable indexes for longevity, fertility and calving ease when they are released for use. Breeders can now place much more trust in the genomic indexes for these traits than they could in the Parent Averages from the past. (Read more: ACCURATE GENETIC EVALUATIONS: Can We Hit the Bull’s-eye?)

Health & Fertility in Total Indexes

Health & Fertility make up 35% in NM$, 33% in the Bullvine’s BPI (Read more: Bullvine Performance Index), 29% in TPI™ and 15% in LPI of the emphasis in these total merit indexes.  The reason for that amount of emphasis is because of their importance to the profitability of operating a dairy farm.

What do Breeders Need to Do?

Breeders need to decide which total merit index best suits their needs.  Some will use only one index while others will use more than one index. No matter which index is used it is always best to corrective mate using the genetic, preferably genomic, index of both the bull and the cow.

For the female side this does require that the herd be milk recorded and type classified and that all females be genomically tested. The expense of recording is a very worthwhile investment to better decision making. Remember new information is continually coming available on genomic results for areas beyond genetic indexes. Parentage verification, heifer management and disease resistance are just the beginning.

The Bullvine Bottom Line

Great forward strides have been made with genomic testing and it is no longer a matter of yes or no in using genetic indexes for Health and Fertility traits. Doubling index accuracy to 55 to 65% is a quantum leap. The future is very bright for enhanced genetic improvement and herd profitability for breeders that use all the tools.


Get original “Bullvine” content sent straight to your email inbox for free.



Leave a Reply

Send this to a friend